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Boid: Rename velocity to direction_vector #68

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Boid: Rename velocity to direction_vector #68

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6656bcc
Boid: Rename velocity to direction_vector
EwoutH Nov 8, 2023
50c0cae
Boid: Remove redundant division
EwoutH Nov 8, 2023
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17 changes: 9 additions & 8 deletions examples/boid_flockers/boid_flockers/boid.py
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ class Boid(mesa.Agent):
- Alignment: try to fly in the same direction as the neighbors.

Boids have a vision that defines the radius in which they look for their
neighbors to flock with. Their speed (a scalar) and velocity (a vector)
neighbors to flock with. Their speed (a scalar) and direction (a vector)
define their movement. Separation is their desired minimum distance from
any other Boid.
"""
Expand All @@ -23,7 +23,7 @@ def __init__(
model,
pos,
speed,
velocity,
direction_vector,
vision,
separation,
cohere=0.025,
Expand All @@ -37,6 +37,7 @@ def __init__(
unique_id: Unique agent identifyer.
pos: Starting position
speed: Distance to move per step.
direction_vector: numpy vector for the Boid's direction of movement. It is a unit vector (a vector with length 1) that determines the direction of the Boid's movement.
heading: numpy vector for the Boid's direction of movement.
vision: Radius to look around for nearby Boids.
separation: Minimum distance to maintain from other Boids.
Expand All @@ -47,7 +48,7 @@ def __init__(
super().__init__(unique_id, model)
self.pos = np.array(pos)
self.speed = speed
self.velocity = velocity
self.direction_vector = direction_vector
self.vision = vision
self.separation = separation
self.cohere_factor = cohere
Expand Down Expand Up @@ -84,7 +85,7 @@ def match_heading(self, neighbors):
match_vector = np.zeros(2)
if neighbors:
for neighbor in neighbors:
match_vector += neighbor.velocity
match_vector += neighbor.direction_vector
match_vector /= len(neighbors)
return match_vector

Expand All @@ -94,11 +95,11 @@ def step(self):
"""

neighbors = self.model.space.get_neighbors(self.pos, self.vision, False)
self.velocity += (
self.direction_vector += (
self.cohere(neighbors) * self.cohere_factor
+ self.separate(neighbors) * self.separate_factor
+ self.match_heading(neighbors) * self.match_factor
) / 2
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The / 2 affects the result. This is self.velocity +=, not self.velocity =.

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Good catch, you're totally right. I will reply in the main thread more extensively.

self.velocity /= np.linalg.norm(self.velocity)
new_pos = self.pos + self.velocity * self.speed
)
self.direction_vector /= np.linalg.norm(self.direction_vector)
new_pos = self.pos + self.direction_vector * self.speed
self.model.space.move_agent(self, new_pos)
4 changes: 2 additions & 2 deletions examples/boid_flockers/boid_flockers/model.py
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Original file line number Diff line number Diff line change
Expand Up @@ -58,13 +58,13 @@ def make_agents(self):
x = self.random.random() * self.space.x_max
y = self.random.random() * self.space.y_max
pos = np.array((x, y))
velocity = np.random.random(2) * 2 - 1
direction_vector = np.random.random(2) * 2 - 1
boid = Boid(
i,
self,
pos,
self.speed,
velocity,
direction_vector,
self.vision,
self.separation,
**self.factors,
Expand Down